The Effect Of Attention On The Process Of Ebbinghaus Illusion

The present research adopted ERP technique to examine the effect of attention on the process of Ebbinghaus illusion in cue target paradigm. Previous researches have demonstrated that attention influences both three-dimensional and two-dimensional size illusion, the perception of three-dimensional figure needs depth cue, and then needs advanced level of processing involved, so attention has an important role in it. While the two-dimensional figure doesn't need depth cue, then what about the effect of attention in it? Experiment one as a preliminary behavior experiment, examined whether attention would influence the process of Ebbinghaus illusion. It adopted 2×2 within-subjects design, the first independent variable was the cue validity(two levels of validity and invalidity); the second was the size of inducing circles(two levels of big and small circles). The results demonstrated that there was a significant interaction between the size of inducing circles and the cue validity, compared with the invalid condition, the valid condition showed that the test circle looked bigger when surrounded by big inducing circles, and looked smaller when surrounded by small inducing circles. This result implied that attention did influence the process of Ebbinghaus illusion in one way, and the process of Ebbinghaus illusion might have different mechanisms between the big and the small inducing circles conditions in another way. The aim of experiment two was to verify the viewpoint that the amplitude of P2 was correlated with the actual perception size of the sphere further with ERP technique. It adopted 2×2×2 within- subjects design, the first independent variable was the cue validity; the second was the size of inducing circles; the third was the location of illusory figure; we analyzed the temporo-occipital electrode in the opposite side of the illusory figure. The results demonstrated that the latency of P1 and N1 in cued condition was earlier than uncued condition, the amplitude of P1 in cued condition was bigger than uncued condition, but the former amplitude of N1 was smaller than the latter, this was in accordance with previous researches. The amplitude of P2 in uncued condition was bigger than cued condition, but the main effect of the inducing circle size and the interaction between it and the cue validity were not significant. In the process of Ebbinghaus illusion, whether the amplitude of P2 is correlated to the perception size of the test circle needs further investigation.